scholarly journals Fermi–LAT Observations toward the Galactic Center

2016 ◽  
Vol 11 (S322) ◽  
pp. 11-20
Author(s):  
Simona Murgia
Keyword(s):  
Dark Matter ◽  
Milky Way ◽  
Galactic Center ◽  
Point Sources ◽  
Source Detection ◽  
Large Area ◽  
Dark Matter Annihilation ◽  
Γ Rays ◽  
Inner Region

AbstractThe inner region of the Milky Way is one of the most interesting and complex regions of the γ-ray sky. Intense interstellar emission and point sources contribute to it, as well as other potential components such as an unresolved population of point sources and dark matter. In recent years, claims have been made of an excess consistent with a dark matter annihilation signal in the data collected with the Fermi Large Area Telescope (Fermi–LAT). Although these results are intriguing, the complexity involved in modeling the foreground and background emission from conventional astrophysical sources of γ-rays makes a conclusive interpretation of these results challenging. In these proceedings, I discuss Fermi–LAT observations of the Galactic center region, the methodology for point source detection and treatment of the interstellar emission, the characterization of the GeV excess, and implications for dark matter.

scholarly journals The Fermi–LAT Galactic Center Excess: Evidence of Annihilating Dark Matter?

2020 ◽  
Vol 70 (1) ◽  
pp. 455-483
Author(s):  
Simona Murgia
Keyword(s):  
Dark Matter ◽  
Cross Section ◽  
Galactic Center ◽  
Dark Matter Particle ◽  
Point Sources ◽  
Current Status ◽  
Large Area ◽  
200 Gev ◽  
Γ Rays ◽  
Particle Nature

The center of the Galaxy is one of the prime targets in the search for a signal of annihilating (or decaying) dark matter. If such a signal were to be detected, it would shed light on one of the biggest mysteries in physics today: What is dark matter? Fundamental properties of the particle nature of dark matter, such as its mass, annihilation cross section, and annihilation final states, could be measured for the first time. Several experiments have searched for such a signal, and some have measured excesses that are compatible with it. A long-standing and compelling excess is observed in γ-rays by the Fermi Large Area Telescope ( Fermi–LAT). This excess is consistent with a dark matter particle with a mass of approximately 50 (up to ∼200) GeV annihilating with a velocity-averaged cross section of ∼10−26 cm3 s−1. Although a dark matter origin of the excess remains viable, other interpretations are possible. In particular, there is some evidence that the excess is produced by a population of unresolved point sources of γ-rays—for example, millisecond pulsars. In this article, I review the current status of the observation of the Fermi–LAT Galactic center excess, the possible interpretations of the excess, the evidence and counterevidence for each, and the prospects for resolving its origin with future measurements.

scholarly journals Could the Fermi Large Area Telescope detect γ-rays from dark matter annihilation in the dwarf galaxies of the Local Group?

2009 ◽  
Vol 496 (2) ◽  
pp. 351-360 ◽  
Author(s):  
L. Pieri ◽  
A. Pizzella ◽  
E. M. Corsini ◽  
E. Dalla Bontà ◽  
F. Bertola
Keyword(s):  
Dark Matter ◽  
Local Group ◽  
Dwarf Galaxies ◽  
Large Area ◽  
Dark Matter Annihilation ◽  
Γ Rays

scholarly journals Illuminating dark matter halo density profiles without subhaloes

2020 ◽  
Vol 499 (2) ◽  
pp. 2426-2444 ◽  
Author(s):  
Catherine E Fielder ◽  
Yao-Yuan Mao ◽  
Andrew R Zentner ◽  
Jeffrey A Newman ◽  
Hao-Yi Wu ◽  
...  
Keyword(s):  
Dark Matter ◽  
Observational Studies ◽  
Cold Dark Matter ◽  
Milky Way ◽  
Matter Density ◽  
Dark Matter Halo ◽  
Dark Matter Annihilation ◽  
Density Profiles ◽  
Matter Component

ABSTRACT Cold dark matter haloes consist of a relatively smooth dark matter component as well as a system of bound subhaloes. It is the prevailing practice to include all mass, including mass in subhaloes, in studies of halo density profiles in simulations. However, often in observational studies satellites are treated as having their own distinct dark matter density profiles in addition to the profile of the host. This difference can make comparisons between theoretical and observed results difficult. In this work, we investigate density profiles of the smooth components of host haloes by excluding mass contained within subhaloes. We find that the density profiles of the smooth halo component (without subhaloes) differ substantially from the conventional halo density profile, declining more rapidly at large radii. We also find that concentrations derived from smooth density profiles exhibit less scatter at fixed mass and a weaker mass dependence than standard concentrations. Both smooth and standard halo profiles can be described by a generalized Einasto profile, an Einasto profile with a modified central slope, with smaller residuals than either a Navarro–Frenk–White or Einasto profile. These results hold for both Milky Way-mass and cluster-mass haloes. This new characterization of smooth halo profiles can be useful for many analyses, such as lensing and dark matter annihilation, in which the smooth and clumpy components of a halo should be accounted for separately.

scholarly journals On a Possible Origin of the Gamma-ray Excess around the Galactic Center

Symmetry ◽  
2021 ◽  
Vol 13 (8) ◽  
pp. 1432
Author(s):  
Dmitry O. Chernyshov ◽  
Andrei E. Egorov ◽  
Vladimir A. Dogiel ◽  
Alexei V. Ivlev
Keyword(s):  
Dark Matter ◽  
Gamma Rays ◽  
Molecular Clouds ◽  
Alternative Explanation ◽  
Gamma Ray ◽  
Galactic Center ◽  
The Self ◽  
Large Area ◽  
Mhd Turbulence ◽  
The Standard Model

Recent observations of gamma rays with the Fermi Large Area Telescope (LAT) in the direction of the inner galaxy revealed a mysterious excess of GeV. Its intensity is significantly above predictions of the standard model of cosmic rays (CRs) generation and propagation with a peak in the spectrum around a few GeV. Popular interpretations of this excess are that it is due to either spherically distributed annihilating dark matter (DM) or an abnormal population of millisecond pulsars. We suggest an alternative explanation of the excess through the CR interactions with molecular clouds in the Galactic Center (GC) region. We assumed that the excess could be imitated by the emission of molecular clouds with depleted density of CRs with energies below ∼10 GeV inside. A novelty of our work is in detailed elaboration of the depletion mechanism of CRs with the mentioned energies through the “barrier” near the cloud edge formed by the self-excited MHD turbulence. This depletion of CRs inside the clouds may be a reason for the deficit of gamma rays from the Central Molecular Zone (CMZ) at energies below a few GeV. This in turn changes the ratio between various emission components at those energies and may potentially absorb the GeV excess by a simple renormalization of key components.

scholarly journals A possible radio signal of annihilating dark matter in the Abell 4038 cluster

2019 ◽  
Vol 495 (1) ◽  
pp. L124-L128 ◽  
Author(s):  
Man Ho Chan ◽  
Chak Man Lee
Keyword(s):  
Dark Matter ◽  
Cross Section ◽  
Radio Signal ◽  
Dark Matter Particle ◽  
Cosmic Ray ◽  
Annihilation Cross Section ◽  
Radio Continuum ◽  
Test Statistic ◽  
Large Area ◽  
Dark Matter Annihilation

ABSTRACT In the past decade, some telescopes [e.g. Fermi-Large Area Telescope (LAT), Alpha Magnetic Spectrometer(AMS), and Dark Matter Particle Explorer(DAMPE)] were launched to detect the signals of annihilating dark matter in our Galaxy. Although some excess of gamma-rays, antiprotons, and electrons/positrons have been reported and claimed as dark matter signals, the uncertainties of Galactic pulsars’ contributions are still too large to confirm the claims. In this Letter, we report a possible radio signal of annihilating dark matter manifested in the archival radio continuum spectral data of the Abell 4038 cluster. By assuming the thermal annihilation cross-section and comparing the dark matter annihilation model with the null hypothesis (cosmic ray emission without dark matter annihilation), we get very large test statistic values >45 for four popular annihilation channels, which correspond to more than 6.5σ statistical preference. This provides a very strong evidence for the existence of annihilating dark matter. In particular, our results also support the recent claims of dark matter mass m ≈ 30–50 GeV annihilating via the bb̄ quark channel with the thermal annihilation cross-section.

scholarly journals The characterization of the gamma-ray signal from the central Milky Way: A case for annihilating dark matter

2016 ◽  
Vol 12 ◽  
pp. 1-23 ◽  
Author(s):  
Tansu Daylan ◽  
Douglas P. Finkbeiner ◽  
Dan Hooper ◽  
Tim Linden ◽  
Stephen K.N. Portillo ◽  
...  
Keyword(s):  
Dark Matter ◽  
Milky Way ◽  
Gamma Ray
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